


Endurance Training

by mariam (yanihops)



Category: Shingeki no Kyojin | Attack on Titan
Genre: Anal Fingering, Anal Sex, Armin is a virgin, Armin is way too tight for him, Bottom Armin Arlert, First Time, Implied Armin Arlert/Eren Yeager, M/M, Make Out Session, Manipulation, Non-Consensual, Reiner Is Hung, Reiner is a big tease, Reiner is supposed to be training Armin not fucking him, Semi-Public Sex, Teasing, Top Reiner Braun, Underage Sex, blowjob, handjob
Language: English
Status: Completed
Published: 2020-05-06
Updated: 2020-05-06
Packaged: 2021-03-03 01:47:40
Rating: Mature
Warnings: Rape/Non-Con, Underage
Chapters: 1
Words: 8,580
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/24036868
Author URL: https://archiveofourown.org/users/yanihops/pseuds/mariam
Summary: Reiner is helping Armin train to become stronger.At least, strong enough to take his dick.
Relationships: Armin Arlert/Eren Yeager, Armin Arlert/Reiner Braun
Comments: 5
Kudos: 205





	Endurance Training

**Author's Note:**

> hey, I haven’t written in a while and this isn’t proofread, but I’m trying my best to improve as a hobbyist in writing. this took me a while and I finished it just now, 4:30 am in my area, with no sleep. I feel like I’ll fit in here. thanks for clicking, enjoy the story (is it still considered a story?)

Reiner frequently assimilated his discipline to Shadis’, but Armin was truly beginning to feel the burn. Today, Armin was tasked with running 3 laps around the entire training grounds, and was put to shame with Reiner running alongside him, with even breathing and light sweat glazing his temporal areas. The tall blonde smiled down at the small cadet, “We’re halfway done with your second lap, come on!” Armin’s brows were furrowed, eyes narrowed at the track still left to cover, his face tinted red and breathing so heavy he felt like he couldn’t support his own chest. 

He would have verbally acknowledged Reiner’s encouragement but he could only forge a small nod. Armin was confident in everything else but his physical prowess, that had been lacking since he was a kid. That is in thanks part to his minimal interest in sports and whatnot. Reiner must have been the type of child to play sports with his father everyday, or hunt two oxen and eat them both on his own; Armin, on the other hand, that being a much smaller and smoother hand, was into books and observing nature to write his observations on the subject in a small and worn leather-bound journal. 

Now being in the survey corps meant he was required to be physically adept for situations he was guaranteed to find himself in... and although playing the tactician was his favoured role, he was trying his best to adapt. Thankfully, Reiner was more than happy to help, and being heavy with muscle and resilient in physical tasks, Armin was rather glad to have him by his side. Certainly better than running alone without encouragement, and Reiner discretely scrutinising Armin’s strength from the sidelines. However, it definitely made Armin a little more than embarrassed knowing Reiner could hear how heavy he was breathing, and see the beads of sweat rolling down his face.

“Almost over, Armin.” Reiner huffed, heavy feet clobbering the dirt beneath them and the grass that had been perfectly flattened from previous laps. When Reiner looked over at the small blond, said blond’s breathing was becoming ragged and fast-paced, making him seem like he was hyperventilating. “Come on, Armin. Breathe even, the second lap is almost over.”

The realization that he was still on his second lap made Armin’s eyes blow wide open and he slowed his running, gradually slumping over until he came to a halt and held onto his knees. Reiner withdrew his next tread and turned back to straighten Armin up, “You were doing so well, man! Look up, catch your breath...” He rubbed Armin’s back up from the lower half, the small blond feeling like his lungs were now expanding. He sighed and held onto Reiner’s forearm, squeezing the tense muscle as he relaxed himself.

“I’m sorry... I was overwhelmed...” Armin panted, plucking the collar of his shirt and dabbing his face with the moist fabric to absorb more sweat than it could probably hold. Reiner bit his lip and continued to soothe his backside, until he audibly heard the teenager’s breathing smooth out. 

“You okay now?” Reiner raised a thin brow and Armin gazed up at him to give a small nod. The taller blond returned the nod and pat his back twice, Armin having to stiffen up to keep from falling face-first. “Alright, well because you fucked up your laps,” Armin frowned, Reiner continued, “you have to redeem yourself with something more intense.”

Armin gasped, anything more intense than this would probably push him to unconsciousness, or death, he thought. Reiner smirked, plotting in his head what Armin believed was his doom. Reiner began to walk again, aiming for a small grove of trees. The small cadet staggered towards Reiner and was just glad to be walking now, at least for a bit before he was potentially killed, and his voice of reason became pleas, “Why more intense? Would it not make sense to ease up on me?” 

Reiner shook his head, “It’ll build your endurance. You need that most of all.” Armin knew not to try negotiating with the guy on fitness matters, and pouted, eyes staring at the ground in front of them. And although Armin knew Reiner did this with him in mind, a part of the boy felt like Reiner had sadistic tendencies that enjoyed seeing the boy suffer. But that probably applied to all men as strong as Reiner, eventually when they get so strong, they must forget that they too were once technically weak. Then they go around thinking boys like Armin can shape up in the matter of a week... but that was Armin’s self-pity sounding off, so he did his best to suck it up and look forward to the improvement that would build. 

Reiner stopped behind a particular tree that was thick at the trunk and stood behind it, away from the general public area of the training grounds. Armin thought peculiarly of Reiner stopping there, and more-so when the man grabbed him by the shoulders and pressed him against the chosen tree. A grunt came from the smaller cadet and he winced before staring up at the heavy-set beast in front of him, “What kind of endurance training is this?” Armin asked with a dubious tone. Reiner covered the situation with a smug smirk and got down to Armin’s height so they were face to face, “You’ll like it.”

The little blond felt Reiner’s hot breath spread over the expanse of his face, causing him to flush a rosy pink across his cheeks, “What if I don’t?” The tall blond raised his brows for a moment of silence but ultimately answered, “You will,” in a tone that inclined Armin to force himself to like whatever was coming his way. And inching towards him was Reiner’s face, and then plastered on his lips were Reiner’s own, and Armin did not know what to do.

One of Reiner’s hands was propped on the trunk of the tree and the other hand held Armin’s cheek, keeping their lips in firm contact and Reiner pressing the blond’s head against the tree in the process. Armin’s hands were bound to the sides of his body, unsure of where they should go, or if he was going to have to wrestle Reiner off of him as a test; his eyes also remained open, watching Reiner’s face in close proximity with nerves quaking his body. Reiner pushed himself off and muttered, “You’re terrible at kissing.”

Armin stiffened up in shock, golden eyes piercing Reiner’s with a twitch, “That’s what that was?!” The taller male stared in disbelief before letting a chuckle rumble through his body, “You’re gonna learn a lot today. You like learning new things right?” Reiner held his chin gently, making sure Armin could not look away, as he loved being washed in the attention of his yellow eyes, that were filled with a mixture of confusion and a spark of interest that he could not get enough of. In fact, he looked forward to seeing a whole new side of Armin today, and the way he would react. Armin nodded at the question, and as soon as he did, he was hoisted up into the air. Reiner was single-handedly holding him up by his ass, and Armin had never felt so tall. He kept himself from wobbling by quickly latching on to Reiner’s bicep and the other hand clutched on his shoulder blade. His supposed trainer smiled at the reaction and was now comfortably facing the boy without having to hunch over, and he remained close enough that he could eat up the squeak Armin let out when he was lifted.

It has become quite clear to Armin what kind of endurance test this would be, but he was unsure of the extents to which Reiner would go. That’s what he was afraid of. He slowly repositioned the hand squeezing Reiner’s bicep to the other shoulder blade as the tall man instructed, “Copy the way that I kiss you. Keep the rhythm.” Armin had such little eagerness and was filled more by unsureness that he waited his head against the tree for Reiner to connect their lips again. The muscular male did just that and made sure to go slowly so Armin could get in sync with his movements. The tiny blond got a feel for the way his lips rolled and understood how he could copy, but he was just too damn shy to cooperate. Reiner quickly parted, “Do what I tell you.” Armin was wracked with nervousness, “I know! I just don’t understand why we can’t do other exercises. This-This won’t help me!” In fact, Armin concluded this would help Reiner more than himself, because he could be the only one actually receiving pleasure; although that was much like the other exercises, there was no mutual benefit to this, from what Armin could tell. Reiner digressed, “Alright, then I guess you don’t want my help?” Armin was quick to dismiss, “Of course I do! I just don’t see how this helps, Reiner! You must understand...”

The man grunted and glared at the blond boy to the point that Armin tried backing in to the tree when he was already pressed against it rather tightly. “Just do what I tell you, then you will understand. Now kiss me back.” This time, Reiner came back with force. It was more difficult for Armin to catch up, but he decided he needed Reiner’s help, even if this wasn’t what he expected. Armin closed his eyes now, solely focusing on the synchronisation of their lips, and Reiner seemed pleased as he backed away for a short second to groan, “That’s it...”, and Armin continued doing what he was doing. The appeal was unknown to Armin, in fact he felt more uncomfortable than not, but he persevered. Reiner then backed away again to direct him, “Wrap your arms around my neck.” Armin did just that. When they continued to make out, he understood why: It deepened their kiss, and made it easier for Reiner to prod at his baby pink lips with the tip of tongue. The new sensation of the wet organ against his lips made Armin’s eyes burst open and move his face away, “Reiner, that’s just nasty!” 

Armin was forced to look at Reiner directly with the hand directing his chin, and then the same grip unlocked his jaw, and his mouth was left wide open. Despite his attempts to close his mouth, Reiner slithered his tongue into the entrance with ease and held Armin’s jaw in place, just in case he would chomp his tongue off or something. When the smaller male’s tongue started to dance with Reiner’s, he released his jaw and opted to rub at the edge of the jawline with his thumb, in soothing circular motions. Their saliva mixed and dripped out of their mouths, and Reiner was losing his composure. Armin could barely breath and was now inhaling deeply from his nose just to keep up. He found the smoothness of their tongues together so uncomfortable he felt his insides cringe, his tongue trying desperately to lick anywhere else, and he decided on Reiner’s teeth. It felt like Reiner smiled lightly against his lips and then began to lick on Armin’s teeth too, specifically his molars and the gums behind them. Armin was rather fascinated by the sharpness of Reiner’s canines, and with the sensations gliding on his gums much more satisfying, he let the tiniest moans roll out of his throat and trap behind his lips. Upon that first drip of sound, Reiner licked it up without a second thought. He wanted more and made sure to explore all the crevices of the blond’s mouth, who now found it hard to explore Reiner’s without their tongue entangling. They’d kissed so much, Reiner had to break apart of a breather, and Armin had to gasp for air, a trail of saliva breaking once they separated. Reiner ogled the glossiness of Armin’s lips and how pink they were from the stimulation, blood certainly livening them up, and Reiner licked his own lips with a desire for more. 

He dove back in before Armin was fully restored of oxygen but this time, without tongue, and basic kissing, but Reiner’s lips were slightly parted, and he kissed slowly to let his teeth graze gently against the texture of Armin’s lips. Now this felt good. Hums of pleasure vibrated in Armin’s throat from the gentle sensations, and Reiner was perfect at balancing the right amount of lips and teeth. Then he took it a step further, holding Armin’s chin again, “Keep your jaw slack.” With that, he slowly placed Armin’s lower lip between his teeth, and began to lightly suck and nibble it, making the blood rush. He could feel it getting sensitive, possibly swelling up, but he actually liked the way it felt. When Reiner backed off, the feeling that remained was close to numbness so it was satisfying. “You like teeth, huh?” Reiner expressed something of pride.

Armin’s face was warm and bashful, and he averted his gaze to the grass below while tightening his grasp on Reiner’s shoulders, “I guess..” That prompted a musical hum from Reiner, perhaps out of teasing or doubt. Either way, it made Armin blush more furiously from before. “Uhuh... Now I want you to guess where else I’m gonna kiss you.” Armin’s breath hitched, and his eyes met Reiner’s with sparkling confusion, “You mean besides the lips?” Reiner hummed “mhm” and placed his lips against Armin’s cheek, pecking it softly as he awaited an answer. Armin rolled his eyes in thought, “Uhm... I-I don’t know.” Reiner groaned, “Get creative.” Armin pursed his lips, thinking where else he could possibly kiss him. That is unless Armin’s fear of Reiner’s plans were true, that this situation would escalate past the point of just making out. If Armin was to be stripped naked, then the possibilities were technically endless. Armin bit his swollen lower lip, and couldn’t stop the thoughts from flooding his mind: how Reiner’s lips would kiss from his face, to his collar bone, chest, stomach, abdomen, and the other god forsaken areas of his body in that pain-staking order of inevitably going lower and lower down his vessel. What embarrassed him further was having to say it out loud, meaning Reiner would probably tease him about his dirty mind. Armin hated this. He didn’t think of himself as dirty, so this was downright demeaning; so much so that Armin felt like what covered him in dirt and grime was not the prior training of today but rather the sexual turn of events that have forced him into a corner.  
“Spit it out. I can tell you’re thinking about it...” Reiner’s gaze lowered down Armin’s small body and to his groin, “You’re getting excited.” 

He groped Armin’s slightly-hardened dick from outside his trousers, making Armin flinch and emit a tiny squeak. “Stop! Don’t touch me there..” Armin whined and gripped the wrist of the hand at his crotch to push it away, but his strength was nothing compared to the man’s before him. Reiner emitted a growl similar to a beast, “Then tell me where I’ll kiss you. You’re smart, this should give you ideas.” Armin strained his brows in a frown and held his breath until he yelped aloud at the way Reiner fondled his member, it enlarging through his pants. He had never been touched down there, the feelings were completely foreign, and inundated him with pleasures he hadn’t known before. Of course he had jacked off in the past, but having someone else do it was completely different; it was more pleasurable, and since you weren’t in control of touching yourself, the pleasure you could get was immeasurable. And Reiner made him feel so damn sensitive, with his calloused hands and the fabrics of his trousers and boxers roughing up his dick, making him feel so good he was still trying to shove his hand off while quiet moans were being forced out of him at the same time.

Reiner seemed to be groaning now too, just at the sight of Armin craning his head back and his swollen lips letting moans escape past them. “Tell me or I’ll skip the kissing part and get straight to fucking the shit out of you.” His words made Armin shiver, and his moan quiver in tone, “Ahh, no... Okay, okay! You’re gonna kiss me- ah- on my neck and my collarbone...” Reiner gave him another kiss on the lips then went down to his neck, nibbling on the sensitive skin while keeping up the act on his clothed dick. Armin dragged his other arm further behind Reiner’s neck and rested his head on the broad shoulder blade, while his other hand maintained a weak grip on Reiner’s wrist that was clearly impossible to control. Every pop of his lips revealed a little pink spot that would most likely disappear by the next day, but the gentleness let Armin feel the true sensitivity of his skin without going numb, and it almost tickles until Reiner’s teeth would sink into the spot and got the blood circulating. “Good, keep going...” Processing his words was getting more difficult, now that he felt Reiner unfastening Armin’s belt and swiping it out of the belt hoops.

A chill crawled up Armin’s spine and a moan that fueled Reiner’s libido slipped as he parted his lips again, “Ah... you’re gonna kiss me on my chest.” Armin recognised the thud to the ground as his belt being dropped. And now, Reiner was unzipping his pants. The blond man snarled, “Be more specific.” He commanded with a firm, deep voice, and just that made it harder to think about anything else but the hand pulling his pants down to his mid-thigh, revealing the bare-skin and leaving Armin exposed in his cotton boxers. Then, Reiner started to fondle the clothed dick again, but this time he was closer than ever to his skin, and the contact made Armin let out a full on moan that made the man he was clutching on to groan lowly and fill his dick with gushing blood. Reiner couldn’t deny the heaviness of his cock now, weighing him down and confined inside his pants. And then Armin tried speaking while he was in the middle of moaning, and it could be attributed to singing a heavenly song in Reiner’s ear, “You’re gonna kiss my nipples...” 

“That’s right. I’m gonna suck on em’ too.” Reiner spoke ruggedly and then let Armin’s feet fall to the floor, the boy surprised to feel so light on them now. In a split second, Reiner was unbuttoning his shirt and ended up forcing the last three apart and slipped it off the blond, revealing his toned and lean chest. His abs weren’t prominent but still tight and defined, and his arms weren’t bulging with muscle but remained rather smooth and lightly toned unlike the frail twigs Reiner thought he was built out of. Reiner found himself affixed on the form of his body, how much tinier Armin was in comparison. And what were the odds he’d be so addicted to the idea of stuffing his cock into the smaller male? Just thinking about how he would even make it fit only made his dick fatter, throbbing to get out of his pants and into the cadet’s cute little bum. 

Reiner thought aloud, “I can’t wait to put my cock in you...” Armin was shocked yet again from being hauled upwards and into Reiner’s arms. This time, he used both hands and secured his palms on both of Armin’s ass cheeks, and raised him up farther against the tree trunk so Reiner was faced with his perked, dusky nipples. He took one in his mouth greedily, and the heat enveloping it now sent Armin on a frenzy. He stared down at Reiner as his nipple was worked on, and felt his face heat up again, and he decided to look away from the scene, deciding on the head of leaves on their tree. “Ahhh... A-Ah, no... please... It’s sensitive... really sensitive...” Armin‘s shyness lulled his moans. When Reiner pulled away from the nipple, the contrast of the heat of his mouth to the atmosphere made it spark up with a cold feeling. Reiner’s tongue made flicking motions on the tip of his nipple and Armin couldn’t hold back the shivering moans. The man did this to both nipples, with Armin embarrassed out of his mind. The most embarrassing part must have been how good it felt. Because he had started out not wanting it, none of this, but his body was contradicting his needs in every way, and now all in his mind was the desire to satisfy the sexual burns searing within his core and filling up his dick to the point of throbbing. As well as pondering Reiner’s words, about putting his cock inside of him... now all he could think about was how that would even work, and if it would feel as good as these gestures, or if it would hurt instead. 

Armin expected to be teased again about another location for Reiner to invade with his mouth, but the blond muttered, “Fuck it, I can’t wait,” and Armin assumed the worst. That which made him tingle, and his cock twitch with want. Reiner put Armin down again and demanded he get on his knees, and Armin followed orders diligently. His bare knees brushed with the dirt and grass but he wasn’t worried about that at the moment. His golden eyes gazed up at the older male, whom now towered over him more than before, casting a shadow that engulfed the tiny cadet in intimidating darkness. Reiner revelled in the innocence that still somehow prevailed in the smaller ones eyes, and was determined to see his eyes express every emotion. Hell, he even wanted to make him cry. Just visualising tears pearling up and rolling down his face, from either a dick in his mouth or being fucked senseless, he would savour every tear, every cry, every whimper... because it’d be him making Armin react that way. They could be out of pleasure or out of pain, and he would only fuck him harder. The times he’d seen him cry before, heard him sob and whine, made Armin seem like an angel, and to be witness to such clarity of emotions through his glassy, large eyes would be like a window into Heaven. All Reiner wanted was to get on the other side. And he needed Armin for that.

“Armin,” but he wondered how much an angel could know about sex, “What do you think I’m gonna make you do now?” He craved to hear the words spill out from his delicate lips. The small blond had his hands positioned one on top of the other between his spread thighs on the grass, his thighs resting on the back of his calves now, making himself even smaller. Reiner wondered if he knew how dirty he looked with a pulsating bulge in his face. “You’re gonna make me...” Armin started, “kiss your crotch?” Although Reiner thought his quote was humorous, he did not laugh. His eyes remained stern and locked on the boy, and he opted to silently unthread his own belt from the hoops and unzipped his trousers, letting them pool at the floor. Armin’s eyes fell onto the bulge, now more obviously pressured in the tight restraints of his boxers, and the heavy thick meat was dripping so much pre-cum it was getting through the fabric. “You can touch it too.” Reiner let Armin steer this part around. The small blond rose to his knees again and had a staring contest with the bulge, his hands hesitantly coming up from their location on the grass.

Armin never thought he’d be touching the cock that he had seen so many times weighing around in the showers, that he would quickly pull his eyes away from despite being fascinated by the size, and yet he was doing that now. He began by kissing the cock through the fabric, and then started using tongue on the roughness. He got a taste of his pre-cum and blinked away the interesting taste, his lashes fluttering, and with red cheeks, he continued to work on his bulge. Besides the bland taste of cloth, his liquids were a little salty and overall had a neutral taste, close to bitter on his tastebuds. Either way, he liked it. And being surrounded by his musk, masculine and pungent, it intoxicated him all around. Reiner above was grunting with every lick, and grabbed the back of Armin’s head to smother his mouth on his own covered cock. “I want you to suck it... you understand?” He yanked on his golden hair, urging the small blond to nod. “And what you can’t take, just work it with your hands.”

Armin cocked his head to the side, but when he pulled off Reiner’s boxers and his cock sprung out, almost smacking him in the face, he knew that his advice would come in handy. The girth of his dick was thick and juicy, probably about the thickness of Reiner’s own forearm, making Armin gulp back the drool salivating in his mouth. Why he was salivating over a gigantic cock? He wouldn’t admit it, but the uncharted territories of sex were starting to intrigue him, and being advised for both fitness and sex by Reiner was starting to peak his fancy. His own cock was bobbing at the thought, of everything Reiner would teach him, and the pleasures he’s felt shocking his body like lightning thus far. To test Reiner’s length, now, Armin pressed the side of his head against the cock in front of him, and they about matched up. He couldn’t stop his hand from going down to his own cock to stroke it. As his focus was on the monster, Reiner was admiring the scene, pumping out hormones every second at the eagerness to get his cock inside Armin’s mouth. Although Reiner was a bit of a tease— correction, the biggest, most perverted tease ever— he was impatient when it came to his own pleasure, and his dick throbbed and twitched as if it had its own mind, trying to get closer to Armin’s lips. Reiner consciously bucked his hip forward so the tip would touch Armin’s lips, and Reiner’s body shook with a deep groan. Armin breathed heavy against the tip, moaning softly from touching himself, and the hot air teased the humidity and heat Reiner would feel on his cock once it was down his throat. 

Subconsciously, Armin licked his lips, and pressed the moistness of them against his head once more, and it sent waves of pleasure rolling throughout Reiner’s body that he could only voice as a buck of the hips to urge Armin to take in more. Armin gave in and sheathed the head in his mouth, but felt himself needing air already. And he had only— Yeah, just his head. Despite being out of breath already, he was making himself more desperate for air when he quickened his pace on pumping his own dick, exhaling deeply out of his nostrils and moans curling out of his throat and vibrating Reiner’s cock, a sensation that was about to become Reiner’s drug. Armin was about to pop his lips off when Reiner pushed his head against the tree behind him, by forcing more of his cock in his mouth. A moan was forced out of him, his jaw felt like it was on the brink of unhinging and falling off, and tears budded in the corners of his eyes, probably because his body thought he was choking. Maybe that was the case. He could not control the pressure on his own cock because of this, and was probably going to suffocate on all the pleasures fuelling his body.

Reiner chimed in, his voice strained and far off in a distant and peaceful island, “Remember, you have to suck it... okay? And use your hands. Fuck...” he cursed under his breath. Armin used his free hand to do as told while using the other for his own, making the sexiest noises that Reiner had basically tuned his ears to listen for at this point. But Armin came to find Reiner’s dick was still pretty dry at the base. “No, Armin, you’ve gotta lubricate the whole thing. Makes handjobs easier. Look,” he informed, which was then followed by him spitting thick saliva down and hoping it landed on his shaft, which, luckily, it did. Armin found it a bit gross but if that was the only way, he supposed, then he took it with an open mind. He put one hand at the base of Reiner’s cock and began spreading around the saliva, but his fingers didn’t even meet because of the circumference of the damn thing. That mental note was a satisfaction on his own. Either way, Armin put both of his hands to work. As he did that, his mouth and tongue were busy tending to his head, circling the tongue around the tip to stimulate all the glands that made Reiner throw his head back. 

“Fuck, that’s good. You can take a little more, can’t you?” Armin was trying to make sounds of disagreement but Reiner proceeded to stick his dick in just a little farther into Armin’s mouth. He made sounds of discomfort as his hands froze in place, trying to adapt to the size. The tall male bit his lip and revelled in the heat that encompassed about a fourth of his dick before pulling out completely. “Just give me a handjob, will you?” Reiner put a hand on Armin’s head and pat it, kneading his fingers on the scalp as if he were a good dog that had just learned to sit. Armin was too busy coughing and gasping for air to answer and simply went with it, using both hands to massage the dick, squeezing from the base, to the tip, and back. Whenever he got to the tip, he would press his thumb on the underside of the head and bring it over the slit before going down again, and made Reiner hiss and tighten his grasp on the golden hair entangled in his fingers. 

Feeling up the size of Reiner’s cock made Armin feel like he could make a mold out of it. There was something amazing about trying to fit it in his mouth and needing to use both hands just to scale the size that excited the little blond to no end. A part of Armin, the curious side, knew the table was open to any questions he wanted to ask. And frankly, he felt like his questions were befitting of their situation. Feeling like oxygen had reached his brain after Reiner’s cock just had, he inquired, “How did you first find out your cock was above average, Reiner?” His tone was airy and hoarse at the same time. Reiner couldn’t imagine the relief of having the pressure of his dick removed from his mouth, and certainly wanted to hear more of his voice, perhaps even listen to what he was saying. “Huh? Sorry, can you repeat that? Ahh, shit...“

“I said, how did you discover your cock was above average?” Armin reiterated, and took Reiner’s head in his mouth again, sucking on the underside and rubbing around the head while pumping the rest of his shaft with the other hand. Reiner raised his brows at the question but grew a self-aware grin not long after. “Back at home— agh— check up at the doc. She told me... You’re a quick learner, holy shit.” Reiner was breathless, and holding back his grunts was impossible. Armin chuckled and retorted, “Yeah, I was forced to,” before sinking his mouth onto the head again, sucking it like you would a lollipop or a creamy fruit popsicle dripping its melted goodness under the sweltering sun-heat. “These are probably the only fun things you’ve ever learned. Am I wrong?”

“Yes, you are.” Armin stated. Reiner snickered and thrust his hips forward to press his tip against Armin’s cheek, dripping over his glowing complexion, “How so?” Reiner quizzed. Armin genuinely smiled for the first time since they started training today and his golden eyes showed a look he’d rarely seen— in fact, a look he’d only seen him show to Eren Yeager— when he spoke, “I learned of the outside world.”

Reiner flinched. Armin took this as a wince of pain and retreated all contact with his hard cock, eyes flashing up at him in alert, “Sorry! Did I hurt you?” Reiner blinked a few times, pure silence shrouding them both. The tall man was not planning on losing his appetite now, so he pushed aside any knowledge of the outside world and glared, “Yeah, watch it on the teeth.” Armin nodded softly and wrapped his dick with his lips and hands again, getting faster with his motions gradually, until Reiner pulled out and secured Armin’s head to the tree trunk by his hair. “That’s good, that was really good.” He panted heavily, putting a hand on the rough bark of the tree to support himself from wobbling onto the floor. The veins in his dick pulsed, and made Armin wonder, “You’re about to cum aren’t you? Let me make you cum.” Those words would have pushed him off the edge if it were not for the fact that he was hooked on the visual of his fat cock in Armin’s tight asshole. It sounded almost painful when Reiner disagreed, “No, not yet. I have two more things I wanna show you.” 

Armin posed no further question and was shortly pulled up from the ground by his arms. Reiner stayed still for a moment, eyes swirling in thought, before smirking, “I have a good fucking idea. Just stay right there.” Armin nodded and watched with sharp eyes as he Reiner got lower to the ground. His face got increasingly redder until Reiner was on his knees, in the same position Armin was moments ago. The man on the ground grabbed Armin’s shirt from earlier— which he was now realising how small it was compared to his own, he’s sure the sleeves would reach the middle of his forearms— and motioned for Armin to slip it on. “Don’t bother buttoning it.” Reiner said. Armin nodded and left his front uncovered. Reiner lifted him up again per usual, but this time, he propped Armin’s legs onto his shoulders, leaving his crotch sitting right in front of Reiner’s face, and Armin’s backside resting against the tree bark, protected by his shirt.

And the older blond gave Armin no room for imagination, as he went straight for putting the smaller cock in his mouth. Armin arched his back and moaned into the air, his legs twitching from finally having proper attention dedicated to his own hard-on. The sounds he was making, on their own, were enough to pump Reiner’s cock for him. Deep throating him was kind of easy, and pressing his tongue on the slit and the underside of his head to abuse his senses were the best way to make him tremble above Reiner. He rolled his hips from pleasure, thrusting deeper into Reiner’s mouth in the process, but Reiner decided to reach up for his hips and hold him back a notch, “Control yourself.” Armin could barely listen. He grabbed a handful of Reiner’s shortly cropped blond hair and pulled with every suck on his head, and pressed his thighs tighter on either side of the man’s head. He ended up using the other hand to cover his mouth with his forearm, biting into his sleeved skin in hopes of quieting down, but Reiner’s ruthlessness made it a more difficult task. Armin’s toes were curling and his member was getting attention it had never received before. But Armin was foolish to think that was where the experience would end.

Armin felt Reiner part from his dick, leaving him shaking and sinking down the tree from opened distance, and heard him spit. That gave him a short window to catch his breath and brush strands of blond hair behind his ear, then Reiner’s hot mouth was back on his dick. Not only that, but something wet prodded at his hole, and he shot up at the feeling, as well as went silent. Then those wet things started digging their way in, and Armin was about screaming. Reiner had to stretch an arm up and cover his mouth up completely. Armin was shaking his head frantically, but Reiner kept going with both of his tasks. When the wet things finally penetrated him, he realised they were Reiner’s fingers, and were wiggling around his tight walls in hopes of getting deeper. But his body was now in disagreement, and he was silently shaking, trying to think about how having things in there made him feel. Reiner looked up at the blond and furrowed his brows slightly, “This is so my cock doesn’t break you in half, alright?” Armin nodded, mouth thankfully still clasped by one of Reiner’s hands, because once Reiner got back to getting his fingers deeper, Armin was screaming again, and desperately reached a hand below him to hold Reiner’s wrist that was currently driving fingers inside him, and used the other hand to tug at the larger male’s hair.

Reiner then decided to add a third digit into Armin’s asshole. As he started to thrust that one in, he felt something wet drip onto the hand covering Armin’s face, and when he looked up, there were tears. His eyes were blank, revealing he was senseless, and his vision was a blur. All he could feel was a mix of pain and pleasure and fighting one feeling while indulging in the other was a difficult thing to do. Little by little, his consciousness was fading, and so his guard was slowly faltering. Reiner smiled at the sight. He was proud to be responsible for stripping Armin of his innocence. And he knew he was one of the luckiest to even be able to touch Armin this way, and be the first to do so. He was shocked Eren hadn’t fucked his little best friend already. Then again, Reiner believed Eren was different from Reiner. In other words, Reiner believed Eren was a better person. And he knew Armin was a great friend, which he’d experienced firsthand, but another side of him was just as interested in his own dirty wishes. This was who Reiner chose to be.

After Armin stopped gripping his wrist and had his fun mewling as Reiner sucked his little cock and fingered him at the same time, he knew the tiny cadet was prepared for him. Or in other words, senseless enough to potentially ignore the pain. He removed his fingers from Armin’s hole and popped his mouth off his dick for the final time. Armin’s eyes were in the stars, but Reiner wanted to take him higher. “Final lesson of the day.” Reiner announced, and Armin seemed to pay his voice no mind. Reiner carried Armin’s legs off of him and instead held him as he had before, hands clutching his ass, but this time he leaned his body back a little bit so they were in an easier position and Reiner had more control over his hips. “This is the best part, Armin. I’ll try my best to make it painless.” Then, Reiner positioned Armin’s hole on the tip of his dick, and that brought the life back into his eyes. He suddenly latched onto Reiner’s shoulders and went close as if he was going to hug him, just as the tip began to sink in.

“AH! R-Reiner, stop! Stop!” But the man in control didn’t listen. Armin had no choice but to hold onto him tight and prepare himself to feel what could be one of the most painful experiences ever or the best experience ever. His facial expression contorted, showing pain as he shut his eyes and knit his brows, and he was so unhinged he did not care to restrain his words, “Ahhhh- Fuck! Reiner, a-ah fuck! Ah god, it hurts! S-Stop!” He pleaded, but Reiner wanted to see how far he could go. Finally, a bit past his head was in. Reiner threw his head back and let out a low moan of his own, biting his lip ravenously. “Reiner, please! S-Slow! Slow down at least! Please!” This time Reiner considered him a little. He slowed his pace but was still lowering Armin onto his cock, and both were feeling the slow, searing stretch of his tight hole. The small blond taking it stuck his nails into Reiner’s backside and scratched as the cock went deeper. Reiner winced and didn’t think when he smacked Armin’s ass so hard it made it sting, glow red, and made the small blond unintentionally ride up on his cock that he was not even close to adjusting to. Armin was struggling to speak now, Reiner thought he might be sobbing. “Hey, look at me.” Reiner commanded. The smaller blond did as told, his yellow eyes pained and shining with tears. “Don’t look away.” The blond nodded obediently, shivering as he anticipated the rest. Reiner watched as his mouth opened in a silent scream and all that escaped was a guttural sob mixed with a moan, and Reiner was pent-up questioning if he should find it as sexy as he did. “There we go... take that cock, you tiny slut.” Reiner muttered that under his breath, not exactly thinking about anything besides the feeling of his cock being squeezed by Armin’s walls. There was still half of his dick still not inserted and he felt like drilling further would be impossible without ripping him apart. And the little one was already crying like hell, so half of his cock should definitely be enough, right? 

“Tell me when I can start fucking you.” Reiner whispered into the boys ear. Armin nodded in understanding and tried controlling his breathing on Reiner’s shoulder to fight his sobs. Minutes passed and Armin was still trembling, except now he was moving his feet softly against Reiner’s back, which was actually quite comforting to the both of them. It prompted Reiner to whisper again, “You okay?” The blond on his shoulder nodded softly, “j-just wait another second... p-please. Please..?” Reiner pressed his lips together, “Of course! Of course, I’m sorry...” Reiner had not prepared for guilt to start weighing on his chest. Armin’s breathing was soft now, and slow, like he was drawing short breaths just to enjoy Reiner’s natural savour, which was working in calming him down, somehow. Reiner felt some movement down there, like Armin was wiggling around to test the waters. And after a little bit, he sent a tiny moan into Reiner’s ear. It was so cute, probably because of its pitchy tone and the softness in how it was delivered. The tall blond knew it was time and didn’t wait to hear his permission, as he fired off into lifting and pushing the boy off and onto his dick halfway, making him make all sorts of sounds at the top of his lungs. Reiner was surprised no one had come to check out their little grove, nor look for the two that had been supposedly training, especially since the sun was beginning to set. They had literally spent the whole day fucking. But Reiner had no regrets, and he was sure Armin would have none neither by the end of it.

“Ah! Ah, fuck... Mm...!” Armin responded well to Reiner’s confident and smooth thrusts. “Ah! Fuck! Reiner- just like that!Ahhh, god!” And he responded just as well to his harder and faster thrusts. Reiner still had trouble fucking into him as the friction was intense but he felt like he could go deeper now. Armin realised immediately, and balled his fists on Reiner’s chest while sobbing out again. His walls were getting tense again, squeezing his cock, “Armin, relax. It’s gonna feel even better, trust me.” But Armin banged against his chest, “No, I can’t! It won’t f-fit... please, I’m fine with not having it all, please!” Reiner continued on his own accord. Armin insides were as tight as a sleeve and smooth like velvet, so going deeper pulled a sigh of satisfaction out of the man. Armin cried out as more of his dick was stuffed in. “S-Stop. Just s-stop...!”

“But don’t you like it when I do this?” And all of sudden, Reiner pulled off from Armin completely, leaving just the tip of his dick against his hole, and he briefly noticed how hollow he felt without Reiner buried deep. But not to worry, because Reiner proceeded to slam his length in its entirety into Armin’s again. Armin screamed out, biting his lip to keep from howling in pain, and held onto Reiner, like his life depended on it, because sadly that’s the only choice he had. The heat from inside of Armin made Reiner feel like he was melting from the inside, and he felt more wet hotness dribbling down onto his abs, when he realised Armin was releasing more pre-cum. “I know you like it when I do that.” Reiner growled into the boy’s ear, and earned himself the sexiest moan of his life, and God must have been spoiling him that day because Armin mewled, “Please, fuck me Reiner.” Reiner did not hesitate to pull out again and start pounding into the tiny cadet, making the boy gasp for air, sob, and yelp out in delectable pleasure with every thrust. Every withdraw and every thrust back in filled their area of the training ground with the sounds of Armin’s ass against Reiner’s pelvis and balls, and him screaming Reiner’s name in a mixture of delight and agony. At least, that’s what Reiner liked to think. 

“Don’t stop! Don’t stop! Reiner! Ah, ah— Reiner!” Reiner never knew Armin could sound so lewd. He had tried imagining what his voice would sound like in his head but nothing came close to how he was in real life. Ever word went straight to his meaty cock, and he was not getting tired of slamming it into his poor little hole. Of course, now it wasn’t so little. “God, your hole is gonna be so stretched out I could fuck you next week and you’d still be gaping for me. Isn’t that right?”

Armin nodded weakly, trying his best to hold on for support. His composure was completely messed up, however, when Reiner pulled off completely again, but instead of doing so to plunge back into him, he changed their position. He set Armin’s feet back on the ground and turned him around, “Hold yourself on the tree and bend over.” Armin nodded and bent over, arching his back in a way that perked his butt up, and put both hands on the tree in front of him. He was such an obedient good boy. Reiner smacked an ass cheek and his hand print stuck like a tattoo, matching the other one on the other cheek from earlier. Seeing as his ass was being so perfectly showcased, Reiner grasped both cheeks and spread them apart; Armin gasped, his hole gaping as large as Reiner thought it was, and contracting from the inside with the cold air from the outside coming into contact. He spit onto the hole just to watch the trail of saliva drip into his already sticky hole. Reiner couldn’t hold back the need to kneel and eat him out quick as possible, sticking his tongue in and swirling around the area he could reach. Then he took three fingers and replaced his tongue with them, using his tongue to instead go down his taint and suckle on his balls. Armin’s legs were shaking so bad that Reiner wrapped an arm around the legs to keep them stiff as he worked on his ass and balls. His skin was so soft and plump to suck on, Reiner wouldn’t mind eating him for dinner like this. But they had to get back soon, or else people would get suspicious. And he did not want to know what Eren nor Mikasa would think about why Armin was out until late with Reiner, who was about two to three times his size and clearly had the upper hand to take advantage of him in any way, which he totally did. So he stood back up and aligned his cock to Armin’s hole, and to do that he had to literally lift Armin’s hips so that his feet weren’t even on the ground anymore, and started back up on an insane pace that Armin could not begin to comprehend.

It was like Armin had forgotten why he was out here having sex with Reiner in the first place. He wondered if his plan was to have sex ever since the first day of training, or if he had the hankering for it today. He wondered if Reiner was technically doing him well by making him feel so good or if he was forced into it and his body had no means of saying no. He wondered many things but all of which he did not have the sense to form answers for. He didn’t know why he was thinking so hard anyway, nor why he started to feel his core tighten, his toes curl, and his back arch. Then he all he knew was pure pleasure, that seemed to last for a while before Reiner started to have his cum milked from his own cock by the contractions of Armin’s hole squeezing around him. He realised he had come all over the grass and shot ropes of cum onto the poor tree, but he had no control. And when Reiner pulled out of him and hollow, cold air filled him instead, his legs trembled so much he would’ve fallen to the ground if Reiner had not caught him.

Armin’s eyes were fluttering, his yellow eyes transitioning from slightly conscious to total blankness. Reiner had no way to tell if he was blissed out or tired as hell, but he did his best to clean off any cum with the back of his own white shirt which would be hidden by the signature cropped jacket they wore as part of regulation. Armin hummed with a slight smile on his face as he felt Reiner smooth the fabric softly over his skin, and Reiner thought he must’ve fallen asleep as soon he finished dressing them both up again. Their uniforms were of course soiled but he was happy the smell of sex would probably be masked by the sweat and grime absorbed in their uniforms.

As he carried the tiny cadet bridal style, his arm hung loosely on his shoulder and head supported by Reiner’s hand to lay on his shoulder, all he could think of was what the fuck were they gonna make up as an excuse for Armin’s limping and would Armin ever train with him again after today? Reiner felt confident that he would. And as for the limping, maybe something about an accident while they were running laps.

**Author's Note:**

> I definitely wanna work more on my writing but this is what I got. thanks for reading my first story PUBLICLY posted on ao3, hope you enjoyed :D !


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